Newswise — In a study that included approximately 15,000 pregnant women, seroprevalence of herpes simplex virus (HSV) type 2 decreased substantially between 1989 and 2010 while there was no overall decrease for HSV type 1, but a slight increase among black women, according to a study in the August 20 issue of JAMA.

Shani Delaney, M.D., and Anna Wald, M.D., M.P.H., of the University of Washington, Seattle, and colleagues examined trends in the seroprevalence of HSV-1 and HSV-2 among pregnant women who delivered newborns at the University of Washington Medical Center between January 1989 and May 2010. The researchers identified 15,738 women with 18,993 pregnancies who had prenatal HSV serological results.

HSV-1 seroprevalence decreased from 69.1 percent during the first decade (1989-1999) to 65.5 percent during 2000-2010, whereas HSV-2 seroprevalence decreased from 30.1 percent to 16.3 percent. After adjusting for various factors, the researchers found no significant annual trend in HSV-1 seroprevalence; however, rates of HSV-2 seroprevalence decreased significantly by 4.8 percent/year. Seroprevalence of HSV-1 increased slightly among black women (0.9 percent/year). Seroprevalence of HSV-2 decreased significantly over time among women of all races; however, rates per year decreased substantially less for black women relative to white women.

The authors note that the decline in HSV-2 seroprevalence does not necessarily avert the potential for neonatal herpes, a rare but serious complication. “Women who are seronegative entering pregnancy and acquire HSV during late pregnancy are at higher risk for transmission of HSV to their infants than seropositive women.”(doi:10.1001/jama.2014.9237; Available pre-embargo to the media at http://media.jamanetwork.com)

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